Water quality is necessary in understanding the health of a river. Tests measure Nitrogen, Phosphorus, Chlorophyll, and Water clarity. Both Nitrogen and Phosphorus are elements that are considered nutrients from all types of runoff. In excessive amounts they can cause algal blooms and affect water clarity. Chlorophyll is a pigment found in plants and algae, and is used to detect suspended phytoplankton (leads to algal blooms). Water clarity tests for suspended sediment and to observe how much sunlight can reach lower lying levels of the river. Pollution can result from both agricultural land, as well as urban, in forms of storm water, runoff, and waste.